EVAPOTRANSPORTATION, CROP COEFFICIENTS, AND LEACHING FRACTIONS OF IRRIGATED DESERT TURFGRASS SYSTEMS

Reducing irrigation volumes on turfgrass in an arid environment requires close attention to environmental demand. The objective of this research was to quantify the water balances of three turfgrass sites controlled by an evapotranspiration (ET) feedback system and local management. Additional objectives included calculating leaching fractions (LF), crop coefficients (Kc), water savings, and quantifying the variability in potential evapotranspiration (ET(o)). A 2-yr study was conducted on three turfgrass sites in southern Nevada growing common bermudagrass [Cynodon dactylon (L.) Pers.) overseeded with perennial ryegrass (Lolium perenne L.). Two vacuum-drained lysimeters and one automated weather station were placed at each location. One lysimeter was irrigated by input from an ET feedback system while the other was left to local management. The daily Penman combination equation was used to calculate ET(o). Hydrologic water balances were maintained on each lysimeter on a weekly basis. A neutron probe was used to measure changes in soil water content in the lysimeters. Actual ET (ET(a)) varied according to management, with the two golf courses having an average ET(a) 29% higher than the park site. Differences in ET(a) between the park site and golf course sites were attributed to cultural management, in particular fertilizer input. Crop coefficients varied on a monthly basis and between high management vs low management turf. A 4 to 6% error was observed in estimating ET(o) among the three sites.